A vehicle such as a wheel loader, backhoe loader, on- or off-highway truck, or the like is normally equipped with a number of wheels. Generally, the wheels are mounted in pairs on an axle. A service brake of a known type is associated with at least one wheel or axle. A parking brake of a known type is also associated with at least one wheel or axle. The service and parking brakes are controlled by an operator. The service brake is generally designed to slow or stop a vehicle in motion. The parking brake is generally designed to hold a stopped vehicle in the stopped position.
Often, an operator will attempt to engage or actuate the parking brake while the vehicle is still moving. If the parking brake is repeatedly used incorrectly to stop the vehicle in this manner, wear of the parking brake components and possible brake failure may result. Therefore it is desirable to provide a method of slowing the vehicle and/or controlling an engagement of the parking brake so as to avoid undue damage to the parking brake.
Hydraulically operated service brakes are common in the industry. Such hydraulically operated brakes require a source of pressurized fluid in order to actuate and disengage the brakes. Proper braking force may not be available if the fluid is not pressurized. The initial start-up of the vehicle is an example of a situation in which fluid in the hydraulic system may not be pressurized. A “pre-fill” period is usually required for sufficient fluid pressure for operation to build up in the hydraulic system supplying the service brakes. If the parking brake is released before pre-fill is completed, the hydraulic service brakes may not be completely operative and the operator may experience a lack of braking force. It would be advantageous to prevent the parking brakes from being disengaged before the service brakes are pre-filled.
U.S. Pat. No. 5,052,532, issued Oct. 1, 1991 to John R. Plate (hereafter referenced as '532) discloses a brake system for a vehicle which includes a pump coupled to a service brake through a brake pedal valve and to a parking brake by a four-way solenoid valve which also couples the pump to a transmission disconnect valve. The '532 invention disconnects the vehicle's transmission so that the vehicle cannot be driven when the parking brake is engaged. However, the extra valve for the transmission disconnect requires extra manufacturing and maintenance effort and may unnecessarily complicate the vehicle's hydraulic system. Also, an operator may desire to engage the parking brake in certain situations to legitimately supplement the service brake, and '532 does not allow for such an application. Additionally, '532 does not monitor the condition of a service brake before allowing the parking brake to be disengaged.
In an embodiment of the present invention, a vehicle is disclosed. The vehicle includes a vehicle body, an operator cab located on the vehicle body, and a ground engaging system. The ground engaging system provides motive power to the vehicle body, and has at least one wheel, at least one service brake and at least one parking brake associated with the wheel, and a braking control system associated with the service brake and the parking brake. The braking control system includes a parking brake control, a speed sensor, and an electronic control module. The parking brake control is adapted to produce a parking brake signal responsive to an operator command. The speed sensor is adapted to produce a vehicle speed signal. The electronic control module is adapted to receive the parking brake signal and the vehicle speed signal and responsively control the service brake such that the service brake is actuated in response to the vehicle speed signal being outside a preferred vehicle speed range.
In an embodiment of the present invention, a braking system is disclosed. The braking system includes a service brake adapted to resist motion of a wheel, a parking brake adapted to resist motion of the wheel, a parking brake control adapted to produce a parking brake signal responsive to an operator command, a ground speed sensor adapted to produce a speed signal responsive to the motion of the wheel, and an electronic control module adapted to receive the parking brake signal and the speed signal and control the service brake responsive to the speed signal being outside a preferred speed range.
In an embodiment of the present invention, a braking system is disclosed. The braking system includes a parking brake adapted to resist motion of a wheel, a parking brake control adapted to produce a parking brake signal responsive to an operator command, a service brake sensor adapted to produce a service brake signal responsive to a ready condition of the service brake, and a parking brake indicator. The braking system also includes an electronic control module adapted to receive the parking brake signal and the service brake signal and control the parking brake indicator responsive to the service brake signal being outside a preferred service brake range.
In an embodiment of the present invention, a vehicle is disclosed. The vehicle includes a vehicle body, an operator cab located on the vehicle body, and a ground engaging system. The ground engaging system provides motive power to the vehicle body, and has at least one wheel, at least one service brake and at least one parking brake associated with the wheel, and a braking control system associated with the service brake and the parking brake. The braking control system includes a parking brake control adapted to produce a parking brake signal responsive to an operator command, a service brake sensor adapted to produce a service brake signal, a speed sensor adapted to produce a vehicle speed signal, and an electronic control module. The electronic control module is adapted to receive the parking brake signal, the service brake signal, and the vehicle speed signal and at least one of: responsively control the service brake such that the service brake is actuated in response to the vehicle speed signal being outside a preferred vehicle speed range, and prevent the parking brake from disengaging in response to the service brake signal being outside a preferred service brake range.